#976 UselessStringValueOf wrong when appending character arrays

[Dominik Seichter]

PMD reports UselessStringValueOf as warning when concatenating a String with a character array. I think the warning is wrong in this case and can lead to bugs when the warning is fixed.

Please see the folloing code snipped:

char[] idFormat = {'0', '0', '0', '0', '0'};
String abc = "1" + String.valueOf(idFormat); // PMD reports a warning here
System.out.println(abc); // Output 100000

So, we fixed the code based on the PMD warning to this:

char[] idFormat = {'0', '0', '0', '0', '0'};
String abc2 = "1" + idFormat; // No warning!
System.out.println(abc2); // Outputs: 1[C@1f8b5b

The reason is that char[].toString() is not equal to String.valueOf(char[]). I think that the UselessStringValueOf rule should not report a warning in this case.

[Steven Christou]

I agree this could be an issue. The addition operator on a [] would point to object references and not content value, and in this instance it will produce a false positive. Can you assign to me to fix? If not I will fix.

[Dominik Seichter]

@christ66: Would be great if you could provide a fix. I cannot assign the issue to you, as you are not in the list "assigned".

[Steven Christou]

Can you check to see if this is still a bug in trunk pmd? I wrote a few test units and they all seem to pass.

[Dominik Seichter]

Hi,

I just checked with latest trunk and still get a warning. I used the following test file:

1:
2: class TestClass {
3:
4: public void testMethod() {
5: char[] idFormat = {'0', '0', '0', '0', '0'};
6: String abc = "1" + String.valueOf(idFormat); // PMD reports a warning here
7: System.out.println(abc); // Output 100000
8: }
9:}

And this command:
_./pmd.sh TestClass.java text ../rulesets/java/strings.xml
/home/dominik/pmd/pmd/bin/TestClass.java:6 No need to call String.valueOf to append to a string.

As you can see, it reports a warning.

[Romain PELISSE]

FYI: I confirm the bug. I can indeed reproduce it.